The present invention relates to an external magnetizing method and an external magnetizing apparatus for rotary electric apparatus using permanent magnets, in which magnetization of metal pieces to a permanent magnetization state is accomplished under the condition that a rotor is situated within the motor yoke.
In general, the magnetization of metal pieces in a rotary electric apparatus to a permanent magnetization state is sometimes accomplished by using an external magnetizing apparatus while the rotor is situated within the motor yoke. Moreover, the conventional external magnetizing apparatus is constructed such that magnetization of the metal pieces which become the permanent magnets is accomplished by applying a power source to a magnetizing coil wound around a magnetizing yoke. However, nowadays, it is desired, with a resulting improved performance of the permanent magnet itself, to apply a high level current for magnetization. It is essential, for this purpose, to enhance the magnetizing efficiency by winding a large diameter magnetizing coil. The magnetizing coil inevitably needs to be large in diameter in order to reduce the resistance of the magnetizing coil for obtaining the necessary current. This results in a disadvantage in that multipolarity (i.e., the magnetization of a plurality of pole magnets) becomes substantially difficult due to interference between an adjacent coil and any cooling apparatus. Consequently, it is only possible to polarize a maximum of about four poles.
It has previously been proposed that a capacitor power source be used in place of a rectifying power source as the magnetizing power source to create the permanent magnets. However, since a capacitor power source can only supply power over a short period of time (unlike the continuous application of power which may be done with a rectifying power source) magnetization is conducted nonuniformly requiring certain countermeasures and a method to solve such problems has not yet been proposed.